Recently, smart grids have become globally popular. For a smart grid, an advanced metering infrastructure (AMI) system has been suggested, whereby various services are provided by means of smart meters connected to a TCP/IP network. For example, with the AMI system, an automatic meter reading (AMR) service in which a remote server acquires metering data from a smart meter via the TCP/IP network and analyzes the acquired data can be realized. In addition, with the AMI system, a demand response (DR) service in which the remote server controls a switch of the smart meter via the TCP/IP network can also be realized.
A networking protocol, the Routing Protocol for Low-power and Lossy Networks (RPL), developed by the Internet Engineering Task Force (IETF) of the International Standards Organization, provides a way of connecting a smart meter to a TCP/IP network. With RPL, smart meters distributed over a wide geographic area form a dynamic multi-hop mesh network and connect to a TCP/IP network.
To achieve secure communication over the multi-hop mesh network, a protocol called Protocol for Carrying Authentication for Network Access (PANA) Relay has been developed by the IETF. With PANA Relay, a key management server that manages encryption keys can securely distribute such keys, thereby enabling secure communication over the TCP/IP network and the multi-hop mesh network.
For the AMI system to provide various services (such as AMR and DR), a fully developed network infrastructure should be in place. Thus, there will be cases where smart meters that cannot independently communicate with remote servers exist locally unless not only the smart meters and remote servers (key management server, AMR server, DR server and so on) forming the AMI system, but also concentrators connecting these devices are deployed in sufficient numbers. In areas where such smart meters exist, various services are unavailable. On the other hand, there may be cases where smart meters are provided prior to installing concentrators while the AMI system has spread. Thus, there may occur isolated areas in which smart meters are already provided but AMI services are unavailable.